Labyrinth-type rotary shaft seals typically include two concentric ring structures which comprise a rotor and a stator. The rotor is sealingly engaged with a rotating shaft and the stator is sealingly engaged with a bearing housing. Many different types of seals have been used to try to seal the space between the spinning rotor and the fixed stator. These include O-rings, rubber lip seals, and labyrinth paths. Labyrinth type seals tend to be the most effective type of seal. Specifically contoured pathways or grooves are formed on the interior surfaces of the seal rings to create a labyrinth extending between the exterior of the bearing housing and the interior of the bearing housing. The labyrinth pathway serves as a hydrodynamic barrier to maintain fluid lubricants within the bearing housing and prevent contaminants from entering the bearing housing. The more elaborate the pathway, the less chance there is that contaminating materials will pass through the structure and into the bearing housing.
In addition, in a typical rotor and stator configuration, some minimum clearance must be maintained to keep the rotor and stator from contacting one another. In some applications, such as aircraft landing gear, the rotor may spin at speeds in excess of about 5000 rpm. If a surface of the rotor contacts a surface of the stator at these speeds, frictional heat develops, the components wear, and the overall efficiency and working life of the apparatus declines. It is, therefore, important to keep the rotor and stator separate.
Further, seals are used to prevent the migration of contaminants from the exterior of the bearing housing and rotor to the interior, as well as prevent loss of lubricating fluid from the interior of the bearing housing and rotor. Contaminants which migrate into the system need to be expelled quickly. Build up of particulate matter within the seal or housing can damage the seal and/or cause increased wear of the rotor and stator. Furthermore, any lubricating fluid forced out of the system must likewise be recaptured and returned to the interior of the rotor. Loss of lubricating fluid will lead to damaged parts and increase the frictional heat of the system
Contaminants which do migrate into the system need to be expelled as quickly as possible. Build up of particulate matter can damage the seal and/or cause increased wear of the rotor and stator. Furthermore, any lubricating fluid forced out of the system must likewise be recaptured and returned to the interior of the rotor. Loss of lubricating fluid will increase the frictional heat of the system and will lead to damaged parts.
It would, therefore, be desirable to provide a labyrinth sealing device with improved particulate exclusion characteristics which would be particularly useful in dusty environments, such as coal pulverizers and cement grinders, as well as an improved capability to reduce the chance or duration of contact between the rotor and stator.
It is to these perceived needs that the present invention is directed.